Coalescence during Emulsification

Single bubble and drop techniques for characterizing foams and emulsions

“…Common bulk foam tests include the industry standard ASTM D892 [20], the foam rise test [21], the shake test [21], and the Flender foam test [22]. Common bulk emulsion tests include the industry standard ASTM D1401 [23], shake test [24], high pressure homogenization (microfluidization) [12,25], and membrane emulsification tests [26]. Detailed reviews on bulk foam and emulsion experiments and the corresponding characterization techniques are available in the literature [21,[26][27][28][29][30][31][32].…”

Coalescence during Emulsification

“…One possible explanation is that the dynamic interfacial tension decreases with increased surfactant concentration, which can facilitate rupture, as is posited by Muller et al (9). However, in Part 2 (20) we have shown, by inference, that when the coalescence of two emulsions is comparable, the variation in interfacial tension does not affect the drop size. That is, the rupture does not depend too strongly on the interfacial tension.…”

“…Because of the relatively high viscosity of the oil phase, the more efficient undecyl pyrene (UDP) was used as the oil soluble fluorescent probe. The reasons for the choice and the synthesis procedure of the probe are described in part I of the series (20).…”

“…For the probe concentration (2%) and mix ratio (1 : 9) chosen, the maximum E/M2 signal is close to 0.95, while complete mixing due to coalescence will reduce the signal to about 0.1. Based on the Monte Carlo simulations discussed in Part 1 of this series (20), E/M2 reaches its lowest value when each drop experiences approximately two coalescence events. Data showing the changes in E/M2, will be referred to as the coalescence data.…”

“…In Part 1 of this series (20) we have described a method that uses an excimer-forming oil soluble fluorescent probe that monitors the amount of coalescence induced mixing. The probe, at a high concentration, is introduced in a fraction of the drops before emulsification.…”